Choose a note to get its equal-tempered frequency, or switch direction and enter any value in hertz to find the nearest note and cents offset. The chart covers C0 through B8 and uses scientific pitch notation, where middle C is C4.
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Convert notes and frequencies
Uses 12-tone equal temperament. Change A4 only when your session or instrument uses another reference.
Need a live reading? Use the Pitch Detector. Need to hear a value? Open the Tone Generator.
C0–B8 at 440 Hz A4
| Oct. | C | C♯ | D | D♯ | E | F | F♯ | G | G♯ | A | A♯ | B |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
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| 8 |
Choose a frequency to load it into the converter. Values use scientific pitch notation, where middle C is C4.
Common musical note frequencies
With A4 set to 440 Hz, middle C (C4) is about 261.626 Hz, A3 is 220 Hz and A5 is 880 Hz. An octave always doubles or halves frequency. The full chart above applies the same relationship to every semitone, so it's more reliable than memorising a short list.
| Note | Frequency at A4 = 440 Hz | MIDI note |
|---|---|---|
| C2 | 65.406 Hz | 36 |
| E2 | 82.407 Hz | 40 |
| A2 | 110.000 Hz | 45 |
| C3 | 130.813 Hz | 48 |
| A3 | 220.000 Hz | 57 |
| C4 (middle C) | 261.626 Hz | 60 |
| A4 | 440.000 Hz | 69 |
| C5 | 523.251 Hz | 72 |
| A5 | 880.000 Hz | 81 |
For piano note frequencies, the 88-key range runs from A0 at 27.5 Hz to C8 at about 4,186.009 Hz in A440 12-TET. Both endpoints are included above; the chart extends farther to C0–B8 for synthesizers, analysis and other instruments. The range and values agree with the current musical-note frequency table maintained for instrument builders.
What A4 = 440 Hz changes
ISO 16:1975 specifies 440 Hz for the tuning note A in the treble stave, and ISO lists the standard as current after its 2022 confirmation. That makes A4 = 440 Hz the sensible default for a general reference chart. It's still a reference, though; it doesn't claim that every ensemble, historical recording or instrument uses the same pitch.
If a session is tuned to A4 = 442 Hz, changing the reference recalculates the entire table. A4 becomes 442 Hz, A3 becomes 221 Hz and A5 becomes 884 Hz. Don't change the field just to make one unstable recording look centred; confirm the reference used by the source first.
How note-to-frequency conversion works
In twelve-tone equal temperament, an octave has a 2:1 frequency ratio and is divided into 12 equal semitone ratios. The UNSW acoustics reference expresses the MIDI-to-frequency conversion as:
frequency = A4 reference × 2(MIDI note − 69) / 12
A4 is MIDI 69. The inverse calculation finds a fractional MIDI position from a frequency. Rounding that position selects the nearest note; the leftover logarithmic distance is reported in cents. One semitone is 100 cents, so 445 Hz at an A4 reference of 440 Hz is still nearest to A4, roughly 19.6 cents sharp.
Why octave labels sometimes disagree
This page uses scientific pitch notation: middle C is C4 and A4 is the reference A above it. Some synthesizers, DAWs and hardware use an octave number one step lower or higher for the same MIDI note. The frequency and MIDI number are the dependable identifiers when labels disagree.
Sharps and flats can also name the same equal-tempered pitch. C♯4 and D♭4 both map to MIDI 61 and the same frequency here. The Sharps/Flats control changes spelling only; it doesn't touch the calculation.
Chart, pitch detector or spectrum analyzer?
| You need to… | Use | Why |
|---|---|---|
| Look up or convert a known note or Hz value | This chart | It performs deterministic 12-TET math without microphone access. |
| Identify one sustained live note | Pitch Detector | It estimates a fundamental from the microphone and reports note, Hz and cents. |
| See several frequencies and harmonics | Spectrum Analyzer | A complex sound contains more than one spectral component. |
| Hear a precise test frequency | Tone Generator | It creates a controlled reference tone after an explicit Play action. |
A spectral peak isn't automatically the note you perceive. Musical sounds commonly include harmonics above the fundamental, and a strong harmonic can be taller than the fundamental in a spectrum. Use the table for known values, the detector for one live pitch and the analyzer when you need the full frequency picture.
Musical note frequency FAQ
What frequency is middle C?
Middle C is C4 in scientific pitch notation. It is approximately 261.626 Hz in twelve-tone equal temperament when A4 is set to 440 Hz, and it is MIDI note 60.
What musical note is 440 Hz?
At the default A4 = 440 Hz reference, 440 Hz is A4 and MIDI note 69. If you change the reference pitch, the same 440 Hz input can sit sharp or flat of the recalculated A4 target.
How do I convert Hz to the nearest note?
Enter the frequency in Hz → Note mode. The calculator finds its fractional position relative to A4, rounds to the nearest equal-tempered note and keeps the remaining distance as cents. A positive value is sharp of the displayed note; a negative value is flat.
Are C-sharp and D-flat the same frequency?
They are enharmonic equivalents in the 12-TET model used here, so C♯ and D♭ share a frequency and MIDI number. Other tuning systems can treat enharmonic spelling and pitch relationships differently.
Why does my synth call middle C C3 instead of C4?
Octave numbering is not universal across instruments and software. This chart uses scientific pitch notation, where middle C is C4. Match the MIDI number or frequency when your device uses another octave-label convention.